重组SAK-HV通过Stat3-C/ebpβ-Pgc-1α途径快速降脂的分子机制研究

Hyperlipemia is the pathogenesis of many diseases, including cerebral-cardio vascular diseases. Recombinant SAK-HV developed by us significantly decreased the serum cholesterol and triglyceride, and improved hepatic steatosis in ApoE-/- mice. Its lipids-lowering effect was significantly better than that of the post-market drug atorvastatin. We found that SAK-HV triggered moderate liver proliferation, accompanied with upregulation of serum IL-6 and activation of both STAT3 and C/ebpβ in liver, as well as the increment of hepatic estrogen level. Meanwhile, the liver transcriptome analysis identified upregulation of both lipids oxidation and hormone synthesis, and further suggested that Pgc-1α was the key effector of the lipid-lowering effect of SAK-HV. Both STAT3 inhibition and Pgc-1α knockout further verified that the direct involvement of STAT3 and Pgc-1α in the rapid lipid-lowering process of SAK-HV. However, the detailed mechanism is unclean. We planed to design experiments based on the liver transcriptome analysis, and make an intensive study about the lipid-lowering mechanism of SAK-HV via a series of experiments based on inhibitors, gene knockout and knock down both in vivo and in vitro. Our research may provide new targets for the treatment against hyperlipemia, and establish foundation for the development of safe and efficient lipid-lowering candidate drugs.

高脂血症是心脑血管等众多疾病的病理基础。我们研制的重组SAK-HV可显著降低ApoE-/-小鼠血胆固醇和甘油三酯，并改善肝脏脂肪沉积。其降脂效果显著优于上市药物阿托伐他汀。研究发现给药组血IL-6升高，肝脏温和增殖，Stat3和C/ebpβ活化，雌激素升高。同时肝脏转录组分析表明脂质氧化以及类固醇激素合成上调，并提示pgc1a可能是SAK-HV降脂效应的关键蛋白。抑制Stat3和敲低Pgc-1α进一步证实它们直接参与了SAK-HV的快速降脂过程，但其详细作用机制未知。我们拟基于肝脏转录组分析设计试验，通过基于抑制剂或基因敲低、敲除的一系列体内外实验深入研究SAK-HV的降脂机制。本研究有望为高脂血症治疗提供新靶点，为安全高效的降脂候选药物研制奠定基础。

高脂血症是心脑血管等众多疾病的病理基础。我们研制的重组SAK-HV可显著降低ApoE-/-小鼠血胆固醇和甘油三酯，并改善肝脏脂肪沉积。其降脂效果显著优于上市药物阿托伐他汀。前期研究证实SAK-HV 通过全新降脂通路Stat3-C/ebpβ-Pgc-1α发挥快速降脂作用，并提示该作用与肝脏温和增殖、补体活化、激素合成上调等有密切关联。本研究中，我们基于上述线索挖掘SAK-HV激活Stat3-C/ebpβ-Pgc-1α降脂通路并发挥快速降脂效应的详细作用机制。我们首次证实Pgc-1α在肝增殖过程中参与肝脏孕、雌激素合成；并创新性地提出补体在肝脏经由Stat3-C/ebpβ-Pgc-1α降脂通路诱导的“Pgc-1α-雌激素”代谢轴构成了肝脏增殖能量模型。在该能量模型中，Pgc-1α作为“点火器”点燃并促进肝细胞活化；Pgc-1α诱导的雌激素作为“点火放大器”增加Pgc-1α的能量供应，进而作为“启动器”触发肝细胞从活化到增殖的状态转变，通过Pparα介导的脂肪酸氧化降低肝脏和血中的甘油三酯胆固醇，并通过Ldlr介导的胆固醇摄取降低血胆固醇水平。该能量模型的提出为肝增殖过程的脂代谢研究提供了新的启示；基于该肝增殖能量模型的独特降脂新策略有潜力成为治疗非酒精性脂肪肝、高胆固醇血症以及高甘油三酯血症的新型短周期生物疗法。然而SAK-HV并未在高脂恒河猴模型体内激活补体系统，且并未产生显著的降脂效应。于是，我们尝试通过免疫增效改善SAK-HV药效，初步证实PLGA-PEG-PLGA（Gel）三嵌段共聚物药物递送系统可以在高脂Apoe-/-小鼠模型中显著增强SAK-HV诱导的免疫水平，为后续改善SAK-HV在大型灵长类动物的降脂药效提供了契机。进一步在体外筛查SAK-HV靶标细胞系，发现SAK-HV通过其SAK突变体功能域增强巨噬细胞增殖效应，其机制是通过抑制MEKK1的自泛素化来激活JNK和ERK MAPK通路促巨噬细胞增殖。我们推测SAK-HV与Uba1的相互作用，可能阻断了Uba1与特定E2酶的交互，从而触发上述途径促进巨噬细胞增殖。此外，SAK-HV能够促进巨噬细胞M1型极化，通过激活JNK/NF-κB通路增强MCP-1表达，从而以自分泌形式促进巨噬细胞迁移。综上所述，本研究有望为高脂血症治疗提供新靶点，为安全高效的降脂候选药物研制奠定基础。

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